This proposal is a competing continuation of a first, multidimensional study of the clinical, psychosocial and biological risk factors for suicidal behavior in patients with Borderline Personality Disorder (BPD), a disorder with a suicide completion rate of 3-9 percent, comparable to affective and schizophrenic disorders. Recurrent suicide attempts, self-injury, and impulsive-aggression are defining characteristics of patients with BPD, related to psychosocial and biologic factors, including childhood histories of abuse and diminished central serotonergic function, measured by CSF monoamine metabolites and the neuroendocrine response to Fenfluramine (FEN). In this study, patients with BPD are compared to depressed patients and normal controls on measures of serotonergic functioning and histories of childhood abuse, in addition to the diagnostic and clinical risk factors previously defined, and followed for 1 year to test the role of these variables as risk factors for suicidal behavior. In a new direction, PET-FDG neuroimaging is introduced during the FEN challenge to measure prefrontal cortical response to serotonergic activation. Patients studied in the original grant period will be followed annually to strengthen the predictor analyses of previously defined risk factors, which include co-morbid depression, substance use disorder, high impulsivity and aggressivity, interpersonal stressors, low social support and absence of psychiatric treatment.